The present invention relates to an insert for an aircraft floor panel, or the like, used to attach the panel to a supporting structure. More particularly, the present insert has the capability to isolate the panel from the vibrational energy propagated through its support.
It has been determined that a large contribution to speech interference level (SIL) noise, in certain commercial aircraft, is radiated by the floor panels. Apparently, the vibration that is transmitted along the beams which support the panels effectively vibrate the panel similar to the way a speaker diaphragm is vibrated. In order to reduce weight, these panels are typically made of an aluminum honeycomb, or other highly rigid constructions, that are highly susceptible to vibration. One current method of attaching these panels to the support beams employs metal inserts that are staked to the floor panel and secured to the upper surface of the support beam using a screw inserted through the insert and threaded into a clip nut. This technique amounts to hard mounting the panel to the support providing a solid path for transmission of vibration.
The present invention significantly reduces SIL noise within the passenger compartment. The attachment insert of the present invention comprises a) a substantially cylindrical rigid outer member secured in an aperture in the floor panel and having an axial throughbore defining a minimum internal dimension of said outer member; b) a contoured elastomeric member bonded to said axial throughbore, said elastomeric member having a central axial opening therethrough and a portion surrounding the central axial opening that extends below a lowermost portion of said outer member; and c) a rigid inner member having a substantially cylindrical first portion of a first diameter which is press fit into said central axial opening of said elastomeric bushing and a shorter cylindrical second portion which has a second larger diameter than said first portion, said second portion generally overlying said contoured elastomeric member, rigid inner member having an axial fastener-receiving throughbore permitting attachment to said support. The outer diameter of the second portion is greater than the minimum internal dimension of the first member. As a result, the insert of the present invention is safetied against possible loss of elastomer integrity. The outer member has a flange which is used to bond the insert to the lower surface of the panel and provides pull-through resistance.
The contoured elastomer has a sleeve portion that extends along the outer periphery of the shank of the inner member and has a longer axial extent than said shank. In addition, the elastomeric member has a solid annulus that extends below the surface of the flange of the outer member. The excessive length of the sleeve results in the elastomer being preloaded in its secured position. The annulus provides a snubbing ring for the panel when the panel is loaded as by a passenger walking, a beverage/food cart, or by carry-on luggage placed beneath the seat. The annulus prevents the loading of the panel from creating a solid path; accordingly, the panel remains isolated from the vibrating support surface such that the SIL noise in the passenger compartment is still reduced.
Various other features, advantages and characteristics of the present invention will become apparent after a reading of the following specification.